Polymorphs of brimonidine pamoate

ABSTRACT

A polymorph of brimonidine pamoate having the formula 
                         
exhibits characteristics disclosed herein. The polymorph is included in a composition, device, or implant for use in the treatment or control of elevated intraocular pressure or in the neuroprotection of components of a neurological tissue to prevent progressive degeneration of such components. In particular, such a composition, device, or implant can be used to provide neuroprotection to cells and components of the optic nerve system.

CROSS-REFERENCE

This application is a divisional of application Ser. No. 13/233,052 filed Sep. 15, 2011, which is a divisional of application Ser. No. 12/604,427, filed Oct. 23, 2009, which claims the benefit of Provisional Patent Application No. 61/115,711 filed Nov. 18, 2008, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to polymorphs of brimonidine pamoate, compositions comprising such polymorphs, and methods of treating or controlling diseases using such polymorphs. In particular, the present invention relates to stable polymorphs of brimonidine pamoate and such compositions comprising such polymorphs for sustained release thereof.

Polymorphism is a property of a substance to exist in more than one solid state crystal structures. The various polymorphic forms—polymorphs—of a crystal have different crystal lattices and, thereby, different physical and chemical properties, such as density, hardness, chemical stability, solubility, rate of dissolution in different solvents, melting point, phase transformation, hygroscopicity, interactions with biological systems, etc. In addition, the term “pseudopolymorphisms” has been applied to different hydrates and solvates of a crystalline material in which water or solvent molecules have been built into the crystal lattice.

Brimonidine, 5-bromo-6-(2-imidazolidinylideneamino)quinoxaline (Formula I), is an α₂ selective adrenergic receptor agonist that has been used in the treatment of open-angle glaucoma by decreasing aqueous humor production and increasing uveoscleral outflow.

For this use, topical ophthalmic solutions have been formulated and the tartrate salt of brimonidine has been used to provide increased solubility of brimonidine. The solubility of brimonidine tartrate is 34 mg/mL in water, and 2.4 mg/mL in a pH 7.0 phosphate buffer while the solubility of brimonidine freebase is negligible in water (see; e.g., U.S. Patent Application Publication 2006/0257452).

Recent studies suggested that brimonidine eye drops may have a neuroprotective effect in a rodent model of ischemic-induced optic nerve cell death. N. O. Danylkova et al., Exp. Eye Res., Vol. 84, 293 (2007); M. P. Lafuente et al., Exp. Eye Res., Vol. 74, 1981 (2002). However, topical application of brimonidine may not be the most effective manner to provide therapeutic effect to neurological tissues in the back of the eye because of the rapid clearance of topically applied compositions.

Intravitreal delivery of brimonidine can provide better access of the drug to the tissues in the back of the eye. Such delivery can be achieved by injecting a liquid-containing composition into the vitreous, or by placing polymeric drug delivery systems, such as implants and microparticles, into the vitreous. Examples of biocompatible implants for placement in the eye have been disclosed in a number of patents, such as U.S. Pat. Nos. 4,521,210; 4,853,224; 4,997,652; 5,164,188; 5,443,505; 5,501,856; 5,766,242; 5,824,072; 5,869,079; 6,074,661; 6,331,313; 6,369,116; and 6,699,493. However, intravitreal administration of drugs should be as infrequent as possible to avoid unnecessary disturbance of the eye.

Therefore, it is very desirable to provide stable brimonidine salts for the preparation of sustained-release compositions. It is also very desirable to provide brimonidine salts that are stable in the vitreous humor. In addition, it is also very desirable to provide such brimonidine salts for duration in ocular environments where they can provide effective neuroprotection to the optic nerve system.

SUMMARY

In general, the present invention provides polymorphs of brimonidine pamoate.

In one aspect, the present invention provides stable or substantially stable polymorphs of brimonidine pamoate.

In another aspect, the present invention provides thermodynamically stable brimonidine pamoate polymorphs.

In another aspect, the present invention provides at least polymorphic forms A, B, C, D, E, and F (as designated herein) of brimonidine pamoate, each having distinguishing characteristics disclosed herein.

In still another aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by an X-ray powder diffraction (“XRPD”) spectrum that comprises peaks at 2θ angles of 7.1, 9.8, 17.8, and 25.5°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by a Raman spectroscopy spectrum that comprises peaks at 145.1, 156.3, 1336.8, 1364.4, and 1412.5 cm⁻¹.

In a further aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by a Raman spectroscopy spectrum that comprises peaks at 1339.9, 1368.7, 1396.1, 1403.1, and 1410.8 cm⁻¹.

In still another aspect, the present invention provides brimonidine pamoate polymorph Form B characterized by an XRPD spectrum that comprises peaks at 2θ angles of 9.7, 14.6, 25.9, and 26.5°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form B characterized by a Raman spectroscopy spectrum that comprises peaks at 1335.6, 1364.6, 1404.4, 1410.7, and 1462.1 cm⁻¹.

In still another aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 12.8, 13.4, and 23.8°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by a Raman spectroscopy spectrum that comprises peaks at 161.5, 1344.8, 1354.1, 1367.9, and 1402.2 cm⁻¹.

In still another aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.5, 12.8, 24.5, and 27.1°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by a Raman spectroscopy spectrum that comprises peaks at 157.4, 1270.4, 1341.5, 1355.5, and 1403.0 cm⁻¹.

In still another aspect, the present invention provides brimonidine pamoate polymorph Form A characterized by an XRPD spectrum that comprises peaks at 2θ angles of 13.5, 20.6, 21.1, and 24.4°±0.2°.

In yet another aspect, the present invention provides brimonidine pamoate polymorph Form A characterized by Raman spectroscopy spectrum that comprises peaks at 1340.8, 1352.4, 1365.8, 1402.0, and 1460.3 cm⁻¹.

In still another aspect, the present invention provides a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof.

In still another aspect, the present invention provides a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms B, C, D, E, F, and combinations thereof.

In a further aspect, the present invention provides a method for treating or controlling glaucoma in a subject. The method comprises administering to an ocular environment of the subject a composition that comprises at least a polymorph of brimonidine pamoate selected from the group consisting of brimonidine pamoate polymorph Forms A, B, C, D, E, F, and combinations thereof. In one embodiment, said treating or controlling is effected by reducing intraocular pressure (“IOP”) in an affected eye of said subject.

In still another aspect, the present invention provides a method for effecting ocular neuroprotection in a subject. The method comprises administering to an ocular environment of the subject a composition that comprises at least a polymorph of brimonidine pamoate selected from the group consisting of brimonidine pamoate polymorph Forms A, B, C, D, E, F, and combinations thereof. In one embodiment, said composition is administered into a posterior segment of an eye of the subject in need of said neuroprotection.

Other features and advantages of the present invention will become apparent from the following detailed description and claims and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an XRPD spectrum of brimonidine pamoate polymorph Form A.

FIG. 2 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form A.

FIG. 3 shows a DSC curve of brimonidine pamoate polymorph Form A.

FIG. 4 shows a TGA curve of brimonidine pamoate polymorph Form A.

FIG. 5 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form A.

FIG. 6 shows An XRPD stack plot of brimonidine hemi-pamoate competitive slurry samples (a) starting material, lot SUC-I-130(1), Form A, (b) lot SUC-I-133(37), Form F, (c) lot SUC-I-138(1), isolated following one week of Forms A, C, D and E slurry in water, (d) lot SUC-I-132(2), Form E, and (e) lot SUC-I-138(2) isolated following one week of Forms A, B, C and D slurry in THF. Patterns (c) and (e) were found to be consistent with patterns (b) and (d), Forms F and E respectively.

FIG. 7 shows an XRPD spectrum of brimonidine pamoate polymorph Form B.

FIG. 8 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form B.

FIG. 9 shows a DSC curve of brimonidine pamoate polymorph Form B.

FIG. 10 shows a TGA curve of brimonidine pamoate polymorph Form B.

FIG. 11 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form B.

FIG. 12 shows an XRPD spectrum of brimonidine pamoate polymorph Form C.

FIG. 13 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form C.

FIG. 14 shows a DSC curve of brimonidine pamoate polymorph Form C.

FIG. 15 shows a TGA curve of brimonidine pamoate polymorph Form C.

FIG. 16 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form C.

FIG. 17 shows an XRPD spectrum of brimonidine pamoate polymorph Form D.

FIG. 18 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form D.

FIG. 19 shows a DSC curve of brimonidine pamoate polymorph Form D.

FIG. 20 shows a TGA curve of brimonidine pamoate polymorph Form D.

FIG. 21 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form D.

FIG. 22 shows an XRPD spectrum of brimonidine pamoate polymorph Form E.

FIG. 23 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form E.

FIG. 24 shows a DSC curve of brimonidine pamoate polymorph Form E.

FIG. 25 shows a TGA curve of brimonidine pamoate polymorph Form E.

FIG. 26 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form E.

FIG. 27 shows an XRPD spectrum of brimonidine pamoate polymorph Form F.

FIG. 28 shows an ¹H NMR spectrum of brimonidine pamoate polymorph Form F.

FIG. 29 shows a DSC curve of brimonidine pamoate polymorph Form F.

FIG. 30 shows a TGA curve of brimonidine pamoate polymorph Form F.

FIG. 31 shows a Raman spectroscopy spectrum of brimonidine pamoate polymorph Form F.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “control” also includes reduction, alleviation, amelioration, and prevention.

As used herein, the term “stable” means incapable of changing in crystalline structure, as exhibited by a plurality of peaks in an XRPD pattern, at a time of two weeks after the initial preparation of the material.

As used herein, the term “neuroprotection” means the rescue of at least some cells or components of a nervous system that are not directly damaged by the primary cause of a disease or injury, but would otherwise undergo secondary degeneration without therapeutic intervention. In one aspect, neuroprotection can lead to preservation of the physiological function of these cells or components. In one aspect, such a nervous system is the optic nerve system. The cells or components of the optic nerve system include those being involved or assisting in conversion of photon to neurological signals and the transmission thereof from the retina to the brain for processing. Thus, the main cells or components of the optic nerve system include, but are not limited to, pigment epithelial cells, photoreceptor cells (rod and cone cells), bipolar cells, horizontal cells, amacrine cells, interplexiform cells, ganglion cells, support cells to ganglion cells, and optic nerve fibers.

In general, the present invention provides polymorphs of brimonidine pamoate.

In one aspect, such polymorphs comprise stable or substantially stable brimonidine pamoate polymorphs.

In another aspect, the present invention provides thermodynamically stable brimonidine pamoate polymorphs.

In still another aspect, the present invention provides at least polymorphic forms A, B, C, D, E, and F (as designated herein) of brimonidine pamoate, each having distinguishing characteristics disclosed herein.

In yet another aspect, the present invention provides at least polymorphic forms B, C, D, E, and F of brimonidine pamoate, each having distinguishing characteristics disclosed herein.

Brimonidine Pamoate Polymorph Form A

In a 5 L 3-neck round bottom flask equipped with overhead stirrer, heating mantle, condenser, temperature probe, and N₂ inlet, 4.8 g of brimonidine (lot 1-080085) was dissolved in ethanol (2000 mL) at 65° C. Pamoic acid (1.05 eq, 19.0 mL, 0.5M in DMSO (dimethyl sulfoxide)) was then added. The resulting solution was stirred for 30 minutes at 65° C. and then cooled at 20° C./hour to ambient temperature. At the onset of the cooling profile, precipitation of solids was observed. The mixture stirred overnight at ambient temperature and was then filtered. The resulting solids were dried under vacuum at ambient temperature for 4 days before being analyzed by XRPD to confirm the solid form, designated as Form A. FIG. 1 shows an XRPD spectrum of brimonidine pamoate polymorph Form A (lot SUC-I-130(1)).

In one aspect, polymorph Form A is characterized by an XRPD spectrum comprising major peaks at 2θ angles of 13.5, 20.6, 21.1, and 24.4°±0.2°.

In another aspect, polymorph Form A is characterized by an XRPD spectrum comprising peaks at 2θ angles of 7.6, 12.2, 12.7, 13.5, 20.6, 21.1, 24.4, 26.5, and 27.7°±0.2°.

¹H NMR analysis of this material showed approximately 3.7 wt % residual ethanol and a 0.5:1 pamoate to brimonidine ratio confirming the formation of a hemi-pamoate salt of brimonidine. FIG. 2 shows an NMR spectrum for brimonidine pamoate polymorph Form A (lot SUC-I-130(1).

Thermal analysis of Form A showed a single DSC endotherm at 221° C. (see FIG. 3) attributed to the melting of the salt and 3.5% TGA weight loss through 190° C. (see FIG. 4) attributed to the removal of ethanol.

FIG. 5 shows a Raman spectroscopy spectrum of Form A (lot SUC-I-130(1), to be compared to Raman spectra of other polymorphs.

In one aspect, polymorph Form A is characterized by a Raman spectroscopy spectrum comprising major peaks at 1340.8, 1352.4, 1365.8, 1402.0, and 1460.3 cm⁻¹.

In another aspect, polymorph Form A is characterized by a Raman spectroscopy spectrum comprising peaks at 135.4, 169.3, 189.2, 233.0, 326.9, 547.9, 693.3, 719.4, 838.3, 938.3, 1031.1, 1197.6, 1252.4, 1270.2, 1340.8, 1352.4, 1365.8, 1402.0, 1460.3, 1549.0, 1556.0, and 1571.0 cm⁻¹.

Moisture sorption analysis of Form A showed this hemi-pamoate polymorph to be slightly hygroscopic, adsorbing 2.2 percent by weight (“wt %”) water at 60 percent relative humidity (“% RH”) and 2.5 wt % water at 90% RH. Upon desorption, no hysteresis or indication of hydrate formation was observed. XRPD analysis of the solids following moisture sorption analysis afforded a diffraction pattern which was consistent with the Form A starting material, indicating no polymorphic form conversion had occurred during the experiment.

Slurries of Form A were prepared in MeOH (methanol), THF (tetrahydrofuran), MIBK (methyl isobutyl ketone), toluene, water and EtOH (ethanol) as described below in an attempt to determine propensity of Form A to undergo form conversion in different solvent systems, as follows. Approximately 15-30 mg of brimonidine hemi-pamoate Form A was weighed into a 1 dram vial and 1.0 mL of solvent (MeOH, THF, MIBK, toluene, water, or EtOH) was added to each vial and allowed to stir magnetically at ambient conditions for three weeks (see summary results in Table 1). Following one week intervals, samples were isolated by centrifugation and dried in vacuo at ambient temperature overnight and analyzed by XRPD to check for polymorphic form conversion.

TABLE 1 Summary of Three Weeks Slurry Experiments Hemi- Hemi- Pamoate Pamoate seeds Form Form Form (Form A) (Form B) Primary Solvent Temperature by XRPD by XRPD by XRPD Lot No. (mg) (mg) (mL) (° C.) (1 week) (2 weeks) (3 weeks) SUC-I-132(1) 32.60 — MeOH 1 Ambient A A A SUC-I-132(2) 31.40 — THF 1 Ambient E E E SUC-I-132(3) 33.30 — MIBK 1 Ambient A A A SUC-I-132(4) 32.30 — Toluene 1 Ambient A A A SUC-I-132(5) 34.20 — Water 1 Ambient A A B (magnetic stirring) SUC-I-132(6) 33.18 — EtOH 1 Ambient A A A SUC-I-132(7) 37.40 — Water 1 Ambient A A n/a (Shaker) SUC-I-132(8) 14.9 1.4 Water 1 Ambient B B n/a n/a—Sample not analyzed

Solids isolated from a slurry of Form A in THF (lot SUC-I-132(2)) following one week of equilibration, afforded a unique XRPD pattern compared to the diffraction patterns of Forms A, B, C, D and F. Further characterization of this unique crystalline solid, designated as Form E, is detailed herein below. These findings indicate that Form E is more stable in THF than Form A. XRPD analysis of solids isolated from a slurry of Form A in water (lot SUC-I-132(5)) following three weeks of equilibration showed conversion to Form B. These findings suggest that Form B is more stable in water than Form A. Form A was also observed to convert to Form B during the aqueous solubility experiment after overnight equilibration in water. As a result, the aqueous solubility of Form A was not determined. No form conversion was observed in the remaining slurry solvents as shown in Table 1.

In an effort to elucidate the relative thermodynamic stability of Form A with respect to the other crystalline forms, competitive slurry experiments were performed as follows. Approximately 15 mg of brimonidine hemi-pamoate Form A and 3 mg of either Forms B, C, D and E were weighed into a 1-dram vial and 1.0 mL of solvent (water or THF) was added (Table 2). Following one week of stirring at ambient conditions, the samples were isolated by centrifugation and dried in vacuo at ambient temperature overnight at 30 inches of Hg. After drying, the samples were analyzed by XRPD to check for form conversion. A one-week slurry comprising Forms A, B, C and D in THF revealed that Form A will convert to the most stable anhydrate form (Form E) as shown in FIG. 6. These findings are consistent with results obtained from the 1 week slurry of Form A in THF. Slurries comprising Forms A, C, D and E in water showed conversion to Form F after one week of equilibration (Table 2). These results indicate that Form F, like Form B, is also relatively stable in water.

TABLE 2 Competitive Slurries of Brimonidine Hemi-Pamoate Forms Weight (mg) SUC-I-130(1) SUC-I-132(8) SUC-I-134(37) SUC-I-134(25) SUC-I-132(2) Solvent Temp XRPD Lo No. (Form A) (Form B) (Form C) (Form D) (Form E) (mL) (° C.) (1 week) SUC-I-138(1) 15.903 — 3.331 3.432 3.501 Water RT Crystalline (1.0) (Form F) SUC-I-138(2) 16.559 3.373 3.819 3.237 — THF RT Crystalline (1.0) (Form E)

The solid state stability of different polymorphs was assessed at elevated temperature and humidity as follows.

Elevated Temperature Stability

Approximately 3-5 mg of brimonidine hemi-pamoate Form A, B, C, D, or E were weighed into individual 1-dram vials and stored uncapped at 60° C. After one week of exposure, the samples were analyzed by XRPD to check for form conversion and HPLC analysis to check for potential degradation. After one week of storage at 60° C., Form A was observed to be stable by XRPD and HPLC (Table 3).

Elevated Humidity Stability

Approximately 1-10 mg of brimonidine hemi-pamoate Form A, F, or C were transferred to vial caps (uncapped) and stored in a closed container with saturated barium chloride dihydrate (BaCl₂.2H₂O). This solution results in 88% RH environment. After two weeks of storage the crystalline form was determined by XRPD and solid inspected for deliquescence. Forms A, C, and F were observed to be stable after two weeks of storage at elevated relative humidity (88% RH), showing no sign of deliquescence or change in crystalline form by XRPD (Table 4).

TABLE 3 Thermal Stress Study of Brimonidine Hemi-Pamoate Forms Starting HPLC Material Weight Temp. XRPD (% Lot No. Lot (Form) (mg) (° C.) (1 week) purity) SUC-I-138(3) SUC-I-130(1) ~3-5 60 Crystalline 100.0 (Form A) (Form A) SUC-I-138(4) SUC-I-132(8) ~3-5 60 Crystalline 100.0 (Form B) (Form B) SUC-I-138(5) SUC-I-133(13) ~3-5 60 Semi- 97.9 (Form C) cryst. (Form C) SUC-I-138(6) SUC-I-134(7) ~3-5 60 Crystalline 96.7 (Form D) (Form D) ¹SUC-I-138(7) SUC-I-138(2) ~3-5 60 Semi- 100.0 (Form E) cryst. (Form E) ¹Sample exposed to elevated conditions for 6 days

TABLE 4 Humidity Chamber Study of Brimonidine Hemi-Pamoate Forms Starting Material Form by Visual Lot(s) % Initial XRPD inspection NB Code (mg) RH Form (2 week) (2 week) SUC-I-136(1) SUC-I-130(1) 88 A A No (25.22) deliquescence SUC-I-136(2) SUC-I-133(37) F F No SUC-I-133(38) deliquescence (4.3) SUC-I-136(3) SUC-I-133(34) C C No (7.4) deliquescence Brimonidine Pamoate Polymorph Form B

Form B was identified at first from a two-week slurry of Form A in water. In addition, Form B was also observed from slow- and fast-cooling (see procedures disclosed below) crystallizations of Form A in DMF/water binary solvent. Form B was fully characterized as described below. FIG. 7 shows an XRPD spectrum of Form B (lot SUC-I-133(36)).

Fast-Cooling Profile

Approximately 20-30 mg of brimonidine hemi-pamoate (lot SUC-I-130(1), Form A) was weighed to a 2-dram glass vial equipped with a stir bar. The starting material was dissolved in a minimal amount (typically 1-7 mL, depending on the ability of the solvent to dissolve the starting solid) of primary solvent at about 55° C. Each solution was passed through a 0.45 μm syringe filter into a preheated vial to remove any undissolved starting material. Following the polish filtration the vials were placed in a refrigerator to achieve a fast cooling rate and left to equilibrate overnight. The following day, the vials were visually inspected for precipitation; those vials with little to no precipitation were gently scratched with a metal spatula to facilitate crystal growth and then allowed to equilibrate an additional 24 hours at 4° C. The resultant solids were either isolated by vacuum filtration or in instances of no precipitation were evaporated to dryness under a gentle stream of nitrogen. All samples were then dried overnight in vacuo at ambient temperature and analyzed by XRPD to determine the solid form.

Slow-Cooling Profile

Approximately 20-30 mg of brimonidine hemi-pamoate (lot SUC-I-130(1), Form A) was weighed to a 2-dram glass vial equipped with a stir bar. The starting material was dissolved in a minimal amount of primary solvent at about 55° C. Each solution was passed through a 0.45 μm syringe filter into a preheated vial to remove any undissolved starting material. Following the polish filtration the samples were cooled to ambient temperature at the rate of 20° C./hour and also allowed to equilibrate overnight. The following day, the vials were visually inspected for precipitation; those vials with little to no precipitation were gently scratched with a metal spatula to facilitate crystal growth and then allowed to equilibrate an additional 24 hours at ambient temperature. The resultant solids were either isolated by vacuum filtration or in instances of no precipitation were evaporated to dryness under a gentle stream of nitrogen. All samples were then dried overnight in vacuo at ambient temperature and analyzed by XRPD to determine the solid form.

In one aspect, polymorph Form B is characterized by an XRPD spectrum comprising major peaks at 2θ angles of 9.7, 14.6, 25.9, and 26.5°±0.2°.

In another aspect, polymorph Form B is characterized by an XRPD spectrum comprising peaks at 2θ angles of 7.0, 9.7, 10.9, 14.6, 19.0, 20.1, 23.4, 25.9, 26.5, and 27.7°±0.2°

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio confirming the formation of a hemi-pamoate salt of brimonidine with approximately 0.1 wt % residual DMF present. FIG. 8 shows an NMR spectrum for brimonidine pamoate polymorph Form B (lot SUC-I-133(36)).

Thermal analysis of Form B showed DSC endothermic events at 76 and 225° C. (see FIG. 9) attributed to loss of residual solvent and melting of the crystalline salt. TGA analysis showed approximately 4.4% weight loss between 50 and 90° C. (see FIG. 10) likely attributed to the loss of water. Karl Fischer analysis of Form B showed 7.2 wt % water. Further characterization by Raman spectroscopy showed major spectral differences compared to anhydrate Forms A, C, D and E while only minor differences were observed compared to Form F. Thus, Form A slowly changed to Form B upon contacting water.

Moisture sorption analysis of lot SUC-I-134(36) showed that Form B adsorbed 5.4 wt % water at 60% RH and 5.8 wt % water at 90% RH. The water content stabilized at around 5-6 t % between 20-90% RH, coinciding with a sesqui-hydrate of brimonidine hemi-pamoate which would theoretically contain 5.4 wt % water. XRPD analysis of the dried solids following the experiment afforded a diffraction pattern which was consistent with Form B, indicating that the dehydrated material had converted back to Form B upon exposure to ambient conditions.

FIG. 11 shows a Raman spectroscopy spectrum of Form B (lot SUC-I-132(8)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form B characterized by a Raman spectroscopy spectrum that comprises peaks at 1335.6, 1364.6, 1404.4, 1410.7, and 1462.1 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoate polymorph Form B characterized by a Raman spectroscopy spectrum that comprises peaks at 106.9, 176.5, 235.4, 379.3, 431.1, 553.6, 694.6, 719.0, 1031.6, 1265.9, 1335.6, 1364.6, 1404.4, 1410.7, 1462.1, and 1579.0 cm⁻¹.

A competitive slurry of Forms (A, B, C and D) in THF revealed that along with the other starting forms, Form B also converted to Form E after one week of equilibration. Form B was observed to be relatively stable in water. This crystalline solid was isolated from a water slurry of Form A after 3 weeks and a mixture of Forms A and B after 1 week (Table 1). Form B was also observed during the aqueous solubility experiment following an overnight slurry of Form A in water (Table 2). The solubility of Form B was determined to be in the range of 0.005-0.02 mg/mL by HPLC. Mixtures of Forms B and Form F were also observed during the solubility experiments from individual slurries of Forms F, C, D and E. A competitive water slurry of Forms A, C, D, and E showed conversion to Form F (Table 2). Subsequent slurry studies demonstrated that aqueous slurries of mixtures of Form B and Form F always resulted in Form B after 7 or 14 days at either 40° C. or room temperature. Thus, Form B is the more stable polymorph in water of the two, both of which are more stable in water than any of the other polymorphs.

Form B was observed to be stable in the solid state after 1 week of storage at 60° C. HPLC and XRPD analysis of the thermally stressed material showed no degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form C

Form C was observed from crystallizations of Form A in binary solvent systems, utilizing the fast cooling profile (disclosed herein above), such as: DMSO/MIBK, NMP (N-methyl-2-pyrrolidone)/acetone, NMP/MTBE (methyl-tort-butyl ether), NMP/EtOH, DMSO/IPAc (isopropyl acetate), NMP/IPA (isopropyl alcohol), and NMP/toluene. Form C was also observed from: NMP/MTBE, DMSO/EtOH, NMP/IPAc, DMSO/IPA, NMP/heptane, NMP/DCM (dichloromethane), NMP/toluene, NMP/water, NMP/THF and NMP/MeOH with a slow cooling profile. This unique solid was fully characterized as described below.

Form C, lot SUC-I-133(34), afforded a unique crystalline XRPD pattern compared to the diffraction patterns of Forms A, B, D, E, and F. FIG. 12 shows an XRPD spectrum of Form C (lot SUC-I-133(34)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 12.8, 13.4, and 23.8°±0.2°.

In another aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 12.8, 13.4, 18.4, 19.2, 19.8, 22.6, and 23.8°±0.2°.

¹H NMR analysis of this material showed approximately 9.9 wt % residual NMP and a 0.5:1 pamoate to brimonidine ratio confirming the formation of a hemi-pamoate salt of brimonidine. FIG. 13 shows an NMR spectrum for brimonidine pamoate polymorph Form C (lot SUC-I-133(34)).

Thermal analysis of Form C showed a single DSC endothermic event at 210° C. (see FIG. 14) attributed to melting of the crystalline salt. Further analysis by TGA showed weight loss of 6.4% between 50 and 140° C. (see FIG. 15) likely due to the loss of water and approximately 7.2 wt % from 180-230° C. (see FIG. 15) attributed to the loss of NMP.

FIG. 16 shows a Raman spectroscopy spectrum of Form C (lot SUC-I-133(25)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by a Raman spectroscopy spectrum that comprises peaks at 161.5, 1344.8, 1354.1, 1367.9, and 1402.2 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoate polymorph Form C characterized by a Raman spectroscopy spectrum that comprises peaks at 135.8, 161.5, 428.7, 720.1, 1031.2, 1270.6, 1344.8, 1354.1, 1367.9, 1402.2, 1461.1, 1549.5, and 1572.7 cm⁻¹.

Raman spectroscopy analysis of Form C showed minor spectral differences in comparison to the Raman spectra of Forms A, D, and E, but significant differences in comparison to the spectra of Forms B and F in the range of about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-134(37) showed the hemi-pamoate to be moderately hygroscopic, adsorbing 4.6 wt % water at 60% RH and 13.0 wt % water at 90% RH. Upon desorption, no hysteresis or indication of hydrate formation was observed. XRPD analysis of the solids following the experiment afforded a diffraction pattern which was consistent with Form C, indicating no form conversion had occurred during the analysis.

A competitive slurry of Forms A, B, C and D in THF revealed that along with the other starting forms, Form C will also convert to the most stable anhydrate form (Form E) (see FIG. 6). Slurries comprising Forms A, C, D and E in water showed conversion to Form F after one week of equilibration (Table 2). These findings indicate that Form F is more stable in water than Forms A, C, D and E. Form C was also observed to convert to a mixture of Forms B and F by XRPD after an overnight slurry in water at ambient conditions. As a result, the aqueous solubility of Form C was not determined.

Form C was observed to be stable after one week of storage at 60° C. HPLC and XRPD analysis of the thermally stressed material showed no significant degradation or signs of form conversion (Table 3). After two weeks of storage at elevated relative humidity (88% RH), Form C was confirmed to be stable by XRPD and showed no indication of deliquescence (Table 4).

Brimonidine Pamoate Form D

Form D was observed from crystallizations of Form A in the following binary solvent systems, using fast-cooling profiles: NMP/MeCN (acetonitrile), DMSO/EtOH and DMSO/toluene. Form D was also isolated from slow-cooling crystallizations such as: NMP/MeCN and NMP/IPA. Form D was fully characterized as described below.

Lots SUC-I-133(35) and SUC-I-133(7) obtained from a fast-cooling crystallizations of Form A in DMSO/toluene and NMP/MeCN, afforded a unique crystalline XRPD pattern compared to the diffraction patterns of Forms A, B, C, E and F. FIG. 17 shows an XRPD spectrum of Form D (lot SUC-I-133(35)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.5, 12.8, 24.5, and 27.1°±0.2°.

In another aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.5, 11.1, 12.8, 18.4, 19.4, 22.5, 23.1, 24.5, 16.4, and 27.1°±0.2°.

¹H NMR analysis of Form D, lot SUC-I-133(35), showed a 0.5:1 pamoate to brimonidine ratio confirming the formation of a hemi-pamoate salt of brimonidine. FIG. 18 shows an NMR spectrum for brimonidine pamoate polymorph Form D (lot SUC-I-133 (35)).

Thermal analysis of Form D, lot SUC-I-133(7), by DSC showed endothermic events at 50 and 206° C. (see FIG. 19) attributed to a loss of residual solvent and melting of the crystalline salt. Further analysis of lot SUC-I-133(35) by TGA showed no weight loss below 160° C. (see FIG. 20).

FIG. 21 shows a Raman spectroscopy spectrum of Form D (lot SUC-I-134(7)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by a Raman spectroscopy spectrum that comprises peaks at 157.4, 1270.4, 1341.5, 1355.5, and 1403.0 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoate polymorph Form D characterized by a Raman spectroscopy spectrum that comprises peaks at 135.7, 146.8, 157.4, 188.9, 328.8, 429.0, 548.8, 720.2, 1030.8, 1253.6, 1270.4, 1341.5, 1355.5, 1403.0, 1461.3, 1549.8, and 1572.6 cm⁻¹.

Raman spectroscopy analysis of Form D showed minor spectral differences in comparison to the Raman spectra of Form A, C, and E, but significant differences in comparison to the spectra of Forms B and F in the range of about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-133(7) showed Form D to be slightly hygroscopic, adsorbing 1.8% water at 60% RH and 2.6 wt % water at 90% RH. Upon desorption no hysteresis or indication of hydrate formation was observed. XRPD analysis of the solids following moisture sorption analysis afforded a diffraction pattern which was consistent with Form D, indicating no form conversion had occurred during the experiment.

A competitive slurry of Forms A, B, C and D in THF revealed that along with the other starting forms, Form D will also convert to the most stable anhydrate form (Form E) (see FIG. 6). Slurries comprising Forms A, C, D and E in water showed conversion to Form F after one week of equilibration (Table 2). These findings indicate that Form F is more stable in water than Forms A, C, D and E. Form D was also observed to convert to a mixture of Forms B and F by XRPD after an overnight slurry in water at ambient conditions. As a result, the aqueous solubility of Form D was not determined.

Form D was observed to be stable after one week of storage at 60° C. HPLC and XRPD analysis of the thermally stressed material showed no significant degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form E

Form E was observed from a one week of slurry of Form A in THF, and later obtained from larger scale slurry of Form A after 18 days.

Form E, lot SUC-I-132(2), afforded a unique crystalline XRPD pattern compared to the diffraction patterns of Forms A, B, C, D and F. FIG. 22 shows an XRPD spectrum of Form E (lot SUC-I-132(2)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

In another aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by an XRPD spectrum that comprises peaks at 2θ angles of 7.7, 8.0, 13.1, and 21.2°±0.2°.

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio confirming the formation of a hemi-pamoate salt of brimonidine which contained approximately 0.2 wt % and 0.3 wt % residual THF and EtOH respectively. FIG. 23 shows an NMR spectrum for brimonidine pamoate polymorph Form E (lot SUC-I-132(2)).

Thermal analysis of Form E showed DSC endothermic events around 71° C. attributed to loss of residual solvent and at 207° C. (see FIG. 24) due to melting of the crystalline salt. Further analysis by TGA showed a 3.7% weight loss between 50 and 150° C. (see FIG. 25) likely attributed to loss of residual THF, EtOH and water.

FIG. 26 shows a Raman spectroscopy spectrum of Form E (lot SUC-I-132(2)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by a Raman spectroscopy spectrum that comprises peaks at 1339.9, 1368.7, 1396.1, 1403.1, and 1410.8 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoate polymorph Form E characterized by a Raman spectroscopy spectrum that comprises peaks at 326.5, 466.6, 549.8, 720.5, 1030.3, 1270.4, 1339.9, 1368.7, 1396.1, 1403.1, 1410.8, 1460.8, and 1573.7 cm⁻¹.

Raman spectroscopy analysis of Form E showed minor spectral differences in comparison to the Raman spectra of Forms A, C, and D, but significant differences in comparison to the spectra of Forms B and F in the range of about 1300-1425 cm⁻¹.

Moisture sorption analysis of lot SUC-I-138(2) showed Form E to be slightly hygroscopic adsorbing 3.1 wt % water at 60% RH and 4.2 wt % water at 90% RH. Upon desorption, no hysteresis or indication of hydrate formation was observed. XRPD analysis of the solids following moisture sorption analysis afforded a diffraction pattern which was consistent with Form E, indicating no form conversion had occurred during the experiment.

A competitive slurry of Forms A, B, C and D in THF revealed that each form converted to the anhydrate Form E. These findings suggest that Form E is the most stable anhydrate form. A slurry comprising Forms A, C, D and E in water showed conversion to Form F after one week of equilibration (Table 2). These findings indicate that Form F is more stable in water than Forms A, C, D and E. Form E was observed to convert to a mixture of Forms B and F by XRPD after overnight slurry in water at ambient conditions. As a result, the aqueous solubility of Form E was not determined.

Form E was observed to be stable after one week of storage at 60° C. HPLC and XRPD analysis of the thermally stressed material showed no significant degradation or signs of form conversion (Table 3).

Brimonidine Pamoate Polymorph Form F

Form F was observed from the following binary solvent crystallizations which utilized fast cooling profiles: NMP/water and DMSO/water. This unique solid form was characterized as described below.

Lots SUC-I-133(37) and SUC-I-133(38) obtained from crystallizations of Form A in NMP/water and DMSO/water solvent systems, using fast-cooling profile (as described herein above), afforded a unique crystalline XRPD pattern compared to the diffraction patterns of Forms A, C, D, and E. The diffraction pattern of Form F showed some similarities to that of the Form B sesqui-hydrate. FIG. 27 shows an XRPD spectrum of Form F (lot SUC-I-136(2)).

In one aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by an X-ray powder diffraction (“XRPD”) spectrum that comprises peaks at 2θ angles of 7.1, 9.8, 17.8, and 25.5°±0.2°.

In another aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by an X-ray powder diffraction (“XRPD”) spectrum that comprises peaks at 2θ angles of 7.1, 9.8, 11.0, 14.1, 17.8, 21.4, 23.7, 25.5, 26.6, 27.6, and 30.0°±0.2°.

A slurry comprising Forms A, C, D, and E in water showed conversion to Form F after one week of equilibration (see FIG. 6). These findings indicate that Form F is more stable in water than Forms A. C. D, and E. A water slurry of Form F left overnight showed the presence of a mixture of Forms B and F. Thus, Form B is the more stable form in water. This was confirmed in subsequent repeated experiments.

¹H NMR analysis showed a 0.5:1 pamoate to brimonidine ratio, confirming the formation of a hemi-pamoate salt of brimonidine and approximately 0.3 wt % residual DMF. FIG. 28 shows an NMR spectrum for brimonidine pamoate polymorph Form F (lot SUC-I-183(1)).

Thermal analysis by DSC showed multiple endothermic events at 68, 216, 228 and 246° C. (see FIG. 29) attributed to loss of water and/or DMF and melting of the crystalline salt. Further analysis of Form F by KF showed approximately 6.2 wt % water and 4.0 wt % loss by TGA (see FIG. 30).

FIG. 31 shows a Raman spectroscopy spectrum of Form F (lot SUC-I-136(2)). This Raman spectrum shows some similarities to Form B (compare FIGS. 11 and 31).

In one aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by a Raman spectroscopy spectrum that comprises peaks at 145.1, 156.3, 1336.8, 1364.4, and 1412.5 cm⁻¹.

In another aspect, the present invention provides brimonidine pamoate polymorph Form F characterized by a Raman spectroscopy spectrum that comprises peaks at 131.4, 145.1, 156.3, 176.6, 235.1, 431.2, 693.8, 718.3, 1336.8, 1364.4, 1412.5, 1440.2, and 1461.7 cm⁻¹.

Moisture sorption analysis of lot SUC-I-183(1) was performed to further confirm the hydration state of Form F. Form F adsorbed approximately 1.8 molar equivalent of water at 40% RH suggesting a di-hydrate of brimonidine hemi-pamoate. XRPD analysis of the solids following the moisture sorption analysis afforded a diffraction pattern which was consistent with Form F, indicating no form conversion had occurred during the experiment.

In another aspect, the present invention provides a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof.

In still another aspect, the present invention provides a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms B, C, D, E, F, and combinations thereof.

In one embodiment, such a pharmaceutical composition comprises an aqueous carrier.

In another embodiment, such a pharmaceutical composition comprises an organic carrier, such as a hydrophobic or a hydrophilic organic material.

In still another embodiment, the pharmaceutical composition comprises brimonidine pamoate polymorph Form B.

In yet another embodiment, the pharmaceutical composition comprises brimonidine pamoate polymorph Form E.

In a further embodiment, the pharmaceutical composition comprises brimonidine pamoate polymorph Form F.

In one aspect, a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof is administered to a subject in need of treatment or control of glaucoma.

In another aspect, a pharmaceutical composition comprising a polymorph of brimonidine pamoate selected from the group consisting of polymorph Forms B, C, D, E, F, and combinations thereof is administered to a subject in need of treatment or control of elevated intraocular pressure.

In still another aspect, the pharmaceutical composition can be used to provide neuroprotection to cells and components of a nervous system. In one embodiment, the nervous system comprises the optic nerve system.

A concentration of at east about 0.3 μg/ml of a brimonidine pamoate polymorph near the site of the damaged tissue is believed adequately to provide therapeutic value for neuroprotection.

In still another aspect, a brimonidine pamoate polymorph is present in the composition in an amount in a range from about 0.0001 to about 95 percent (weight by volume). As used herein, the phrase “1 percent (weight by volume),” for example, means 1 gram in 100 ml of the composition. In one embodiment, the brimonidine pamoate polymorph is present in the composition in an amount in a range from about 0.0005 to about 75 percent (weight by volume), or alternatively, from about 0.001 to about 50, or from about 0.001 to about 25, or from about 0.001 to about 10, or from about 0.001 to about 5, or from about 0.001 to about 1, or from about 0.001 to about 0.5, or from about 0.002 to about 0.2, or from about 0.005 to about 0.1 percent (weight by volume).

In yet another aspect, a brimonidine pamoate polymorph is present in the composition in an amount in a range from about 0.0001 to about 95 percent (by weight of the total composition). In one embodiment, the brimonidine pamoate polymorph is present in the composition in an amount in a range from about 0.0005 to about 75 percent by weight, or alternatively, from about 0.001 to about 50, or from about 0.001 to about 25, or from about 0.001 to about 10, or from about 0.001 to about 5, or from about 0.001 to about 1, or from about 0.001 to about 0.5, or from about 0.002 to about 0.2, or from about 0.005 to about 0.1 percent by weight.

In one embodiment, a composition of the present invention is in a form of a suspension or dispersion. In another embodiment, the suspension or dispersion is based on an aqueous solution. For example, a composition of the present invention can comprise micrometer- or nanometer-sized particles of the complex suspended or dispersed in sterile saline solution. In another embodiment, the suspension or dispersion is based on a hydrophobic medium. For example the micrometer- or nanometer-sized particles of the complex can be suspended in a hydrophobic solvent e.g., silicone oil, mineral oil, or any other suitable nonaqueous medium for delivery to the eye. In still another embodiment, the micrometer- or nanometer-sized particles of the complex can be coated with a physiologically acceptable surfactant (non-limiting examples are disclosed below), then the coated particles are dispersed in a liquid medium. The coating can keep the particles in a suspension. Such a liquid medium can be selected to produce a sustained-release suspension. For example, the liquid medium can be one that is sparingly soluble in the ocular environment into which the suspension is administered. In still another embodiment, the complex is suspended or dispersed in a hydrophobic medium, such as an oil. In still another embodiment, such a medium comprises an emulsion of a hydrophobic material and water. In still another embodiment, the insoluble complex disclosed herein can be dosed by any normal drug delivery vehicle including but not limited to suspension in a liposome formulation (both within and outside the liposome wall or strictly outside the liposome core), in the continuous phase of an emulsion or microemulsion, in the oil phase of the emulsion, or in a micellar solution using either charged or uncharged surfactants. A micellar solution wherein the surfactant is both the micelle forming agent and the anion of the complex disclosed herein would be preferable.

In another aspect, a composition of the present invention can further comprise a non-ionic surfactant, such as polysorbates (such as polysorbate 80 (polyoxyethylene sorbitan monooleate), polysorbate 60 (polyoxyethylene sorbitan monostearate), polysorbate 20 (polyoxyethylene sorbitan monolaurate), commonly known by their trade names of Tween® 80, Tween® 60, Tween® 20), poloxamers (synthetic block polymers of ethylene oxide and propylene oxide, such as those commonly known by their trade names of Pluronic®; e.g., Pluronic® F127 or Pluronic® F108)), or poloxamines (synthetic block polymers of ethylene oxide and propylene oxide attached to ethylene diamine, such as those commonly known by their trade names of Tetronic®; e.g., Tetronic® 1508 or Tetronic® 908, etc., other nonionic surfactants such as Brij®. Myrj®, and long chain fatty alcohols (i.e., oleyl alcohol, stearyl alcohol, myristyl alcohol, docosohexanoyl alcohol, etc.) with carbon chains having about 12 or more carbon atoms (e.g., such as from about 12 to about 24 carbon atoms). Such compounds are delineated in Martindale, 34^(th) ed., pp. 1411-1416 (Martindale, “The Complete Drug Reference,” S. C. Sweetman (Ed.), Pharmaceutical Press, London, 2005) and in Remington, “The Science and Practice of Pharmacy,” 21^(st) Ed., p. 291 and the contents of chapter 22, Lippincott Williams & Wilkins, New York, 2006). The concentration of a non-ionic surfactant, when present, in a composition of the present invention can be in the range from about 0.001 to about 5 weight percent (or alternatively, from about 0.01 to about 4, or from about 0.01 to about 2, or from about 0.01 to about 1, or from about 0.01 to about 0.5 weight percent). Any of these surfactants also can be used to coat micrometer- or nanometer-sized particles, as disclosed above.

In addition, a composition of the present invention can include additives such as buffers, diluents, carriers, adjuvants, or other excipients. Any pharmacologically acceptable buffer suitable for application to the eye may be used. Other agents may be employed in the composition for a variety of purposes. For example, buffering agents, preservatives, co-solvents, oils, humectants, emollients, stabilizers, or antioxidants may be employed.

Water-soluble preservatives which may be employed include sodium bisulfite, sodium bisulfate, sodium thiosulfate, benzalkonium chloride, chlorobutanol, thimerosal, ethyl alcohol, methylparaben, polyvinyl alcohol, benzyl alcohol, phenylethyl alcohol, peroxide (such as hydrogen peroxide, urea hydrogen peroxide, or a source that generate a peroxide compound such as perborate), biguanide compounds, and quaternium compounds (such as polyquat-1, polyquat-10, etc.). These agents may be present in individual amounts of from about 0.001 to about 5 percent by weight (preferably, about 0.01 to about 2 percent by weight).

Suitable water-soluble buffering agents that may be employed are sodium carbonate, sodium borate, sodium phosphate, sodium acetate, sodium bicarbonate, etc., as approved by the United States Food and Drug Administration (“US FDA”) for the desired route of administration. These agents may be present in amounts sufficient to maintain a pH of the system of between about 5 and about 8. As such, the buffering agent may be as much as about 5 percent on a weight to weight basis of the total composition. Electrolytes such as, but not limited to, sodium chloride and potassium chloride may also be included in the formulation. Physiologically acceptable buffers include, but are not limited to, a phosphate buffer or a Tris-HCl buffer (comprising tris(hydroxymethyl)aminomethane and HCl). For example, a Tris-HCl buffer having pH of 7.4 comprises 3 g/l of tris(hydroxymethyl)aminomethane and 0.76 g/l of HCl. In yet another aspect, the buffer is 10× phosphate buffer saline (“PBS”) or 5×PBS solution.

Other buffers also may be found suitable or desirable in some circumstances, such as buffers based on HEPES (N-{2-hydroxyethyl}piperazine-N′-{2-ethanesulfonic acid}) having pK_(a) of 7.5 at 25° C. and pH in the range of about 6.8-8.2; BES (N,N-bis{2-hydroxyethyl}2-aminoethanesulfonic acid) having pK_(a) of 7.1 at 25° C. and pH in the range of about 6.4-7.8; MOPS (3-{N-morpholino}propanesulfonic acid) having pK_(a) of 7.2 at 25° C. and pH in the range of about 6.5-7.9; TES (N-tris{hydroxymethyl}-methyl-2-aminoethanesulfonic acid) having pK_(a) of 7.4 at 25° C. and pH in the range of about 6.8-8.2; MOBS (4-{N-morpholino}butanesulfonic acid) having pK_(a) of 7.6 at 25° C. and pH in the range of about 6.9-8.3; DIPSO (3-(N,N-bis{2-hydroxyethyl}amino)-2-hydroxypropane)) having pK_(a) of 7.52 at 25° C. and pH in the range of about 7-8.2; TAPSO (2-hydroxy-3{tris(hydroxymethyl)ethylamino}-1-propanesulfonic acid)) having pK_(a) of 7.61 at 25° C. and pH in the range of about 7-8.2; TAPS ({(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino}-1-propanesulfonic acid)) having pK_(a) of 8.4 at 25° C. and pH in the range of about 7.7-9.1; TABS (N-tris(hydroxymethyl)methyl-4-aminobutanesulfonic acid) having pK_(a) of 8.9 at 25° C. and pH in the range of about 8.2-9.6; AMPSO(N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid)) having pK_(a) of 9.0 at 25° C. and pH in the range of about 8.3-9.7; CHES (2-cyclohexylamino)ethanesulfonic acid) having pK_(a) of 9.5 at 25° C. and pH in the range of about 8.6-10.0; CAPSO (3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid) having pK_(a) of 9.6 at 25° C. and pH in the range of about 8.9-10.3; or CAPS (3-(cyclohexylamino)-1-propane sulfonic acid) having pK_(a) of 10.4 at 25° C. and pH in the range of about 9.7-11.1.

In one aspect, the composition has a pH that is suitable for administration into a subject; e.g., to render the composition non-irritating. For example, for topical ophthalmic administration, a desired pH is in the range from about 5 to about 8.

In one aspect, the composition has a pH of about 7. Alternatively, the composition has a pH in a range from about 7 to about 7.5.

In another aspect, the composition has a pH of about 7.4.

In yet another aspect, a composition also can comprise a viscosity-modifying compound designed to facilitate the administration of the composition into the subject or to promote the bioavailability in the subject. In still another aspect, the viscosity-modifying compound may be chosen so that the composition is not readily dispersed after being administered into an ocular environment (such as the ocular surface, conjunctiva, or vitreous). Such compounds may enhance the viscosity of the composition, and include, but are not limited to: monomeric polyols, such as, glycerol, propylene glycol, ethylene glycol; polymeric polyols, such as, polyethylene glycol; various polymers of the cellulose family, such as hydroxypropylmethyl cellulose (“HPMC”), carboxymethyl cellulose (“CMC”) sodium, hydroxypropyl cellulose (“HPC”); polysaccharides, such as hyaluronic acid and its salts, chondroitin sulfate and its salts, dextrans, such as, dextran 70; water soluble proteins, such as gelatin; vinyl polymers, such as, polyvinyl alcohol, polyvinylpyrrolidone, povidone; carbomers, such as carbomer 934P, carbomer 941, carbomer 940, or carbomer 974P; and acrylic acid polymers. In general, a desired viscosity can be in the range from about 1 to about 400 centipoises (“cp” or mPa·s).

In another aspect, the present invention provides a method for producing a composition comprising a brimonidine pamoate polymorph selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof (or alternatively, polymorph Forms B, C, D, E, F, and combinations thereof), the method comprising: (a) providing said brimonidine pamoate polymorph; and (b) dispersing an amount of said polymorph in a sufficient amount of said medium to produce said composition to achieve a predetermined concentration of said polymorph in said medium. Alternatively, a portion of the polymorph remains in a solid phase for a period longer than 2 days, or 1 week, or 1 month, or 2 months, or 3 months, or 4 months, or 5 months, or 6 months, or 1 year, or 2 years after said polymorph has been in contact with said medium. In one embodiment, the method can optionally include a step of reducing the size of the polymorph before dispersing such polymorph in the medium.

In still another aspect, the present invention provides a method for producing brimonidine pamoate polymorph Form B or F. The method comprises: (a) producing brimonidine pamoate polymorph Form A; (b) contacting said polymorph Form A with water for a time sufficient to convert said polymorph Form A to polymorph Form B or F.

In still another aspect, the present invention provides a method for producing brimonidine pamoate polymorph Form B or F. The method comprises: (a) producing brimonidine pamoate polymorph Form A, C, D, E, or a combination thereof; (b) contacting said polymorph Form A, C, D, E, or combination thereof with water for a time sufficient to convert said polymorph Form A, C, D, E, or combination thereof to polymorph Form B or F.

In yet another aspect, the present invention provides a method for producing brimonidine pamoate polymorph Form E. The method comprises: (a) producing brimonidine pamoate polymorph Form A; (b) contacting said polymorph Form A with THF for a time sufficient to convert said polymorph Form A to polymorph Form E.

In a further aspect, the present invention provides a method for producing brimonidine pamoate polymorph Form E. The method comprises: (a) producing brimonidine pamoate polymorph Form A, B, C, D, or a combination thereof; (b) contacting said polymorph Form A, B, C, D, or combination thereof with THF for a time sufficient to convert said polymorph Form A, B, C, D, or combination thereof to polymorph Form E.

In another aspect, a formulation comprising a brimonidine pamoate polymorph selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof (or alternatively, polymorph Forms B, C, D, E, F, and combinations thereof) is prepared for topical administration, periocular injection, or intravitreal injection. An injectable intravitreal formulation can desirably comprise a carrier that provides a sustained-release of the active ingredients, such as for a period longer than about one day, or one week, or longer than about 1, 2, 3, 4, 5, or 6 months, or 1 or 2 years. In certain embodiments, the sustained-release formulation desirably comprises a carrier that is insoluble or only sparingly soluble in an ocular environment (such as the ocular surface, conjunctiva, or vitreous). Such a carrier can be an oil-based liquid, emulsion, gel, or semisolid. Non-limiting examples of oil-based liquids include castor oil, peanut oil, olive oil, coconut oil, sesame oil, cottonseed oil, corn oil, sunflower oil, fish-liver oil, arachis oil, and liquid paraffin.

In one aspect, a composition of the present invention can be administered into a subject in need of neuroprotection at one time or over a series of treatments. A composition of the present invention may be administered locally; e.g., intravitreally by intrabulbar injection for ocular neuroprotection, or by intrathecal or epidural administration for spinal protection. Many of the compositions of the invention can be administered systemically; e.g., orally, or intravenously, or by intramuscular injection. In addition, compositions for protection of the retina and optic nerve that are capable of passing through the cornea and achieving sufficient concentration in the vitreous humor (such as a concentration disclosed herein above) may also be administered topically to the eye. In one embodiment, the neuroprotection can prevent progressive damage to cells or components of the optic nerve, which damage results from glaucoma, retinitis pigmentosa, AMD, diabetic retinopathy, diabetic macular edema, or other back-of-the-eye diseases.

In one embodiment, a composition of the present invention can be injected intravitreally, for example through the pars plana of the ciliary body, to treat or prevent glaucoma or progression thereof, or to provide neuroprotection to the optic nerve system, using a fine-gauge needle, such as 25-30 gauge. Typically, an amount from about 25 μl to about 100 μl of a composition comprising a brimonidine pamoate polymorph disclosed herein is administered into a patient. A concentration of such a polymorph is selected from the ranges disclosed above.

In still another aspect, a brimonidine pamoate polymorph selected from the group consisting of polymorph Forms A, B, C, D, E, F, and combinations thereof (or alternatively, polymorph Forms B, C, D, E, F, and combinations thereof) is incorporated into an ophthalmic device or system that comprises a biodegradable material, and the device is injected or implanted into a subject to provide a long-term (e.g., longer than about 1 week, or longer than about 1, 2, 3, 4, 5, or 6 months, or 1 or 2 years) treatment or prevention of glaucoma or progression thereof or to provide neuroprotection to the optic nerve system. In some embodiments, the ophthalmic device or system can comprise a semipermeable membrane that allows the complex to diffuse therethrough at a controlled rate. In still some other embodiments, such a controlled rate provides a supply of the complex over an extended period of time at or near the site of desired treatment. Such a device system may be injected or implanted by a skilled physician in the subject's ocular or periocular tissue.

Some compositions of the present invention are disclosed in the examples below. It should be understood that the proportions of the listed ingredients may be adjusted for specific circumstances.

EXAMPLE 1

TABLE 1 Ingredient Amount Carbopol 934P NF 0.25 g Purified water 99.75 g Propylene glycol 5 g EDTA 0.1 mg Brimonidine pamoate polymorph Form B 100 mg

An appropriate proportion of EDTA (e.g., shown in Table 1) is added to purified water in a stainless steel jacketed vessel that is equipped with a stirring mechanism. An appropriate amount of carbopol 934P NF is added, over a period of five to ten minutes to form a substantially uniform dispersion. Propylene glycol is added to the resulting mixture while mixing for three to ten minutes. Then, an appropriate amount to brimonidine pamoate having polymorph Form B, which may be previously micronized, is added to the contents of the vessel over a period of three to five minutes while mixing continues until the compound is substantially dispersed. The pH of the mixture is adjusted to 7-7.5 using 1 N NaOH or 1 N HCL solution. The final composition is sterilized, using, for example, heat or radiation and then packaged in appropriate containers.

EXAMPLE 2

A procedure similar to that disclosed in Example 1 is used to produce the composition of the present invention having the ingredients listed in Table 2.

TABLE 2 Amount (% by weight, except Ingredient where “ppm” is indicated) Povidone 1.5 HAP (30%) 0.05 Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form F 0.5 Alexidine 2HCl 1-2 ppm Purified water q.s. to 100 Note: “HAP” denotes hydroxyalkyl phosphonates, such as those known under the trade name Dequest ®. HAPs can be used as chelating agents and have been shown to inhibit bacterial and fungal cell replication.

EXAMPLE 3

A procedure similar to that disclosed in Example 1 is used to produce the composition of the present invention having the ingredients listed in Table 3.

TABLE 3 Amount (% by weight, except Ingredient where “ppm” is indicated) Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form E 0.25 Alexidine 1-2 ppm Sunflower oil q.s. to 100

EXAMPLE 4

A modification of the procedure disclosed in Example 1 is used to produce the composition of the present invention having the ingredients listed in Table 4.

An appropriate proportion of polysorbate 80 (e.g., shown in Table 4) is added to approximately 20 percent of the desired final volume of purified water in a stainless steel jacketed vessel that is equipped with a stirring mechanism. Glycerin and propylene glycol are then added to the mixture while mixing continues for five more minutes. To a sterilized second vessel, heated to about 80° C. and equipped with a stirring mechanism, containing approximately 70 percent of the desired final volume of purified water, an appropriate amount of CMC-MV is added over a period of three to five minutes while mixing continues until the CMC forms a substantially uniform solution. The contents of the second vessel are cooled to about room temperature and then the contents of the first vessel are transferred into the second vessel. The remaining of the desired volume of purified water is added to the second vessel. Then, appropriate amounts of brimonidine pamoate polymorphs Form B and Form F are added to the contents of the second vessel over a period of three to five minutes while mixing continues until the drugs are substantially uniformly dispersed. The pH of the mixture is adjusted to 7-7.5 using 1 N NaOH or 1 N HCl solution. The final composition is sterilized, using, for example, heat or radiation, and packaged in appropriate containers.

TABLE 4 Amount (% by weight, except Ingredient where “ppm” is indicated) Carboxymethyl cellulose, medium 0.5 viscosity (“CMC-MV”) Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form B 0.3 Brimonidine pamoate polymorph Form F 0.3 Polysorbate 80 ® (a surfactant) 0.25 Alexidine 2HCl 1-2 ppm Purified water q.s. to 100

EXAMPLE 5

A procedure similar to that of Example 1 is used to produce a composition comprising the ingredients listed in Table 5.

TABLE 5 Amount (% by weight, except Ingredient where “ppm” is indicated) Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form E 0.5 Tween ® 80 0.25 Alexidine 1-2 ppm Corn oil q.s. to 100

EXAMPLE 6

A procedure similar to that of Example 4 is used to produce a composition comprising the ingredients listed in Table 6.

TABLE 6 Amount (% by weight, except Ingredient where “ppm” is indicated) CMC (MV) 0.5 Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form B 0.75 Brimonidine pamoate polymorph Form A 0.75 Tyloxapol (a surfactant) 0.25 Alexidine 2HCl 1-2 ppm Purified water q.s. to 100

EXAMPLE 7

A procedure similar that of Example 1 is used to produce a composition comprising the ingredients listed in Table 7.

TABLE 7 Amount (% by weight, except Ingredient where “ppm” is indicated) HPMC 0.5 Glycerin 3 Propylene glycol 3 Brimonidine pamoate polymorph Form A 0.6 Brimonidine pamoate polymorph Form C 0.6 Brimonidine pamoate polymorph Form D 0.6 Tyloxapol (a surfactant) 0.25 Alexidine 2HCl 1-2 ppm Purified water q.s. to 100

Alternatively, purified water may be substituted with an oil, such as fish-liver oil, peanut oil, sesame oil, coconut oil, sunflower oil, corn oil, or olive oil to produce an oil-based formulation comprising a brimonidine pamoate polymorph.

Benefits of brimonidine pamoate polymorphs, or compositions comprising the same, of the present invention for neuroprotection can be determined, judged, estimated, or inferred by conducting assays and measurements, for example, to determine: (1) the protection of nerve cells from glutamate induced toxicity; and/or (2) the neural protection in a nerve crush model of mechanical injury. Non-limiting examples of such assays and measurements are disclosed in U.S. Pat. No. 6,194,415, which is incorporated herein by reference.

The following sections disclose the instrumentation and procedures used in applicable experiments disclosed hereinabove.

Instrumentation

Instrument Name and Model Number Differential Scanning Calorimeter Mettler 822^(e) DSC Thermal Gravimetric Analyzer Mettler 851^(e) SDTA/TGA X-Ray Powder Diffraction System Shimadzu XRD-6000 Moisture-Sorption Analysis IGAsorp Moisture Sorption Instrument Nuclear Magnetic Resonance 500 MHz Bruker AVANCE Spectrometer High-Performance Liquid Waters Alliance Chromatography Raman Spectrometer Kaiser RXN1 Differential Scanning Calorimetry

Differential scanning calorimetry (“DSC”) analyses were carried out on the samples “as is”. Samples were weighed in an aluminum pan, covered with a pierced lid, and then crimped. Analysis conditions were 30° C. to 30-300 or 350° C. ramped at 10° C./minute.

Thermal Gravimetric Analysis

Thermal gravimetric analysis (“TGA”) analyses were carried out on the samples “as is”. Samples were weighed in an alumina crucible and analyzed from 30° C. to 230° C. at 10° C./minute.

X-Ray Powder Diffraction

Samples for x-ray powder diffraction (“XRPD”) were analyzed “as is”. Samples were placed on Si zero-return ultra-micro sample holders and analyzed using the following conditions:

X-ray tube: Cu Kα, 40 kV, 30 mA Slits Divergence Slit 1.00 deg Scatter Slit 1.00 deg Receiving Slit 0.30 mm Scanning Scan Range 3.0-45.0 deg Scan Mode Continuous Step Size 0.04° Scan Rate 2°/minute Moisture-Sorption Analysis

Moisture sorption analysis was performed on brimonidine hemi-pamoate starting material at 25° C. from 40 to 90% relative humidity (“RH”) for the adsorption scan, from 85 to 0% RH from the desorption scan and 10 to 40% RH to complete the adsorption scan. Approximately 10 mg of the sample was analyzed in a Pyrex bulb. Each scan utilized a step size of 10% RH and a maximum equilibration time of four hours per point. The sample was dried for one hour at 80° C. following the desorption scan to obtain the dry sample weight and then it was analyzed by XRPD.

Nuclear Magnetic Resonance

Samples (˜2 to 10 mg) of brimonidine hemi-pamoate were dissolved in DMSO-d₆ with 0.05% tetramethylsilane (“TMS”) for internal reference. ¹H NMR spectra were acquired at 500 MHz using 5 mm broadband observe (¹H—X) Z gradient probe. A 30 degree pulse with 20 ppm spectral width, 1.0 s repetition rate, and 16 to 128 transients were utilized in acquiring the spectra.

High Performance Liquid Chromatography

Instrument Parameters:

-   Column: Agilent Eclipse XDB-C18, 4.6×150 mm -   Mobile Phase A: 0.05% TFA in water -   Mobile Phase B: 0.05% TFA in MeCN -   Flow Rate: 1.0 mL/min -   Column Temperature Ambient -   Detection: 248 nm -   Diluent: MeOH -   Injection Volume: 5 μl

Gradient Conditions Time (minutes) % A % B 0 90 10 10 80 20 15 10 90 22 90 10 Raman Spectroscopy

Samples for Raman spectroscopy analysis were analyzed “as is”. Samples were placed in a 96 well plate and analyzed using the following conditions:

Raman Source: 785 nm laser Objective: 1.2 mm PHaT Single Exposure Time: 12 seconds Co-Additions: 12 Enabled Exposure Options: Cosmic Ray filtering Dark Subtraction Intensity Calibration Peak Data List for FIG. 1.

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 4.2466 20.79077 187 18 0.2185 1121 2 7.6046 11.61596 306 29 0.2754 2445 3 7.9817 11.06798 92 9 0.2701 645 4 8.4780 10.42114 49 5 0.2132 287 5 10.2865 8.59267 71 7 0.2589 516 6 10.6400 8.30797 50 5 0.3288 568 7 12.2376 7.22673 310 29 0.2694 2347 8 12.6551 6.98924 370 35 0.2541 2532 9 13.5142 6.54680 708 67 0.2539 5267 10 15.9242 5.56101 407 39 0.2813 3253 11 17.2082 5.14885 95 9 0.2814 759 12 17.5600 5.04649 69 7 0.2200 432 13 17.9600 4.93498 56 5 0.2172 304 14 18.2926 4.84600 82 8 0.3587 798 15 19.0500 4.65500 46 4 0.2200 337 16 20.5858 4.31105 536 51 0.3056 4728 17 21.1359 4.20007 1054 100 0.3147 8574 18 21.6400 4.10336 61 6 0.2400 656 19 22.3600 3.97283 53 5 0.1530 195 20 22.6778 3.91787 184 17 0.3008 1664 21 23.7822 3.73837 180 17 0.2685 1282 22 24.3653 3.65021 465 44 0.4763 5402 23 25.2130 3.52937 79 7 0.3140 668 24 25.7958 3.45094 80 8 0.2583 533 25 26.5170 3.35870 339 32 0.2629 2795 26 26.9200 3.30933 94 9 0.0000 0 27 27.1600 3.28062 100 9 0.0000 0 28 27.6643 3.22196 312 30 0.4589 3993 29 28.3600 3.14448 65 6 0.1930 466 30 29.0700 3.06927 143 14 0.3480 1289 31 29.7594 2.99972 106 10 0.4469 1420 32 31.4704 2.84042 147 14 0.2799 1309 33 31.8800 2.80486 46 4 0.0000 0 34 32.1600 2.78107 72 7 0.2934 648 35 33.1200 2.70262 45 4 0.4960 606 36 33.5373 2.66994 82 8 0.3253 653 37 34.1811 2.62111 78 7 0.4378 800 38 34.5200 2.59615 40 4 0.2400 340 39 36.0203 2.49138 44 4 0.5860 625 40 36.6483 2.45012 37 4 0.4033 315 41 37.4400 2.40011 54 5 0.2156 476 42 37.6800 2.38537 50 5 0.0000 0 43 38.0000 2.36602 43 4 0.0000 0 44 38.2000 2.35409 35 3 0.4000 291 45 38.5600 2.33294 33 3 0.8444 427 46 39.5569 2.27641 43 4 0.2088 237 47 40.1748 2.24281 88 8 0.2845 753 48 40.8706 2.20622 42 4 0.1922 236 49 41.1614 2.19130 44 4 0.2229 259 50 41.5793 2.17024 32 3 0.1925 184 Peak Data List for FIG. 7

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 3.1200 28.29512 60 5 0.0960 176 2 6.6400 13.30110 77 7 0.1214 486 3 6.9590 12.69208 346 31 0.2045 1993 4 9.2400 9.56338 40 4 0.1334 331 5 9.6919 9.11846 1125 100 0.1549 5388 6 10.0800 8.76824 64 6 0.0972 469 7 10.9152 8.09912 328 29 0.1651 1745 8 11.2000 7.89380 43 4 0.1500 350 9 12.8400 6.88901 45 4 0.2666 407 10 13.0646 6.77108 112 10 0.1853 481 11 13.9829 6.32839 133 12 0.2059 900 12 14.6097 6.05827 464 41 0.2178 2875 13 15.8563 5.58467 115 10 0.1547 678 14 16.3336 5.42253 210 19 0.2007 1304 15 16.9123 5.23827 40 4 0.1398 227 16 17.7200 5.00128 137 12 0.1692 693 17 17.9200 4.94591 168 15 0.1926 807 18 18.4065 4.81627 78 7 0.1570 399 19 19.0254 4.66096 347 31 0.1579 1626 20 19.4563 4.55870 172 15 0.1734 856 21 20.1020 4.41370 309 27 0.1757 1429 22 20.4080 4.34821 68 6 0.2240 415 23 20.7623 4.27480 153 14 0.1809 711 24 21.0242 4.22214 183 16 0.1742 949 25 21.9600 4.04428 122 11 0.1724 647 26 22.1600 4.00823 204 18 0.1576 817 27 22.4400 3.95885 69 6 0.1472 367 28 23.3503 3.80653 386 34 0.1740 1895 29 24.0046 3.70424 91 8 0.1416 432 30 25.0920 3.54612 219 19 0.1582 1114 31 25.4804 3.49294 122 11 0.1325 429 32 25.9362 3.43258 437 39 0.1842 2312 33 26.4632 3.36540 364 32 0.2195 2126 34 26.8834 3.31375 185 16 0.2629 1292 35 27.4400 3.24778 63 6 0.0868 201 36 27.6748 3.22076 312 28 0.1980 2113 37 27.9600 3.18855 167 15 0.0000 0 38 28.2000 3.16196 86 8 0.1600 1020 39 28.8839 3.08863 136 12 0.1444 489 40 29.1200 3.06412 93 8 0.1790 571 41 29.8002 2.99571 36 3 0.2075 277 42 30.2953 2.94787 176 16 0.2227 1128 43 31.0177 2.88084 56 5 0.1511 254 44 31.8400 2.80829 76 7 0.1544 462 45 32.0919 2.78682 105 9 0.2202 638 46 32.7087 2.73566 43 4 0.1375 260 47 34.4000 2.60493 34 3 0.1400 318 48 36.0075 2.49224 71 6 0.1650 510 49 36.3455 2.46984 53 5 0.1257 223 50 36.8388 2.43789 59 5 0.1483 269 Peak Data List for FIG. 12

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 3.1600 27.93705 12 4 0.0400 12 2 3.4220 25.79866 39 12 0.1025 103 3 3.7040 23.83511 88 27 0.2962 670 4 4.8400 18.24300 10 3 0.0572 13 5 6.6933 13.19530 14 4 0.1067 46 6 7.1200 12.40544 23 7 0.1236 122 7 7.3600 12.00144 50 16 0.2000 289 8 7.6582 11.53478 218 68 0.2728 1412 9 8.4163 10.49740 32 10 0.2073 216 10 9.2650 9.53763 13 4 0.1700 79 11 9.6339 9.17323 12 4 0.1835 94 12 11.1323 7.94165 59 18 0.3446 617 13 11.9947 7.37253 63 20 0.2106 478 14 12.8351 6.89163 321 100 0.2454 2388 15 13.4414 6.58210 203 63 0.3724 2174 16 13.9943 6.32327 45 14 0.2114 284 17 14.3866 6.15171 10 3 0.1467 41 18 14.9013 5.94036 31 10 0.2712 230 19 15.4581 5.72762 71 22 0.3438 633 20 15.9600 5.54862 53 17 0.3134 506 21 16.9566 5.22468 39 12 0.1721 218 22 18.3959 4.81902 171 53 0.2237 1257 23 19.1563 4.62941 109 34 0.2102 725 24 19.8131 4.47740 117 36 0.2315 796 25 20.5843 4.31136 10 3 0.0886 48 26 20.9200 4.24293 15 5 0.1900 91 27 21.3600 4.15651 88 27 0.3658 577 28 21.6000 4.11087 48 15 0.5120 430 29 22.1600 4.00823 30 9 0.3200 282 30 22.6435 3.92373 121 38 0.2281 746 31 23.0400 3.85709 15 5 0.1226 144 32 23.4800 3.78580 41 13 0.1090 133 33 23.7994 3.73571 216 67 0.2887 1711 34 24.4000 3.64510 41 13 0.2934 455 35 25.0440 3.55281 37 12 0.2480 262 36 25.8800 3.43991 42 13 0.1280 277 37 26.4800 3.36331 41 13 0.0000 0 38 27.0221 3.29705 82 26 0.2708 1269 39 27.4800 3.24315 62 19 0.0000 0 40 27.7600 3.21107 34 11 0.4228 493 41 28.3200 3.14883 35 11 0.2312 166 42 28.5200 3.12720 39 12 0.2488 228 43 28.9543 3.08128 16 5 0.2286 95 44 29.3227 3.04340 63 20 0.3196 528 45 30.2600 2.95123 26 8 0.2000 159 46 30.5457 2.92427 10 3 0.1314 29 47 30.8000 2.90071 15 5 0.0700 24 48 31.0600 2.87701 22 7 0.3600 206 49 31.4413 2.84299 14 4 0.1093 46 50 32.0800 2.78783 28 9 0.1334 125 Peak data List for FIG. 17

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 7.0800 12.47543 14 7 0.1600 119 2 7.5471 11.70433 212 100 0.3942 2076 3 8.5000 10.39422 6 3 0.2000 29 4 10.3000 8.58144 8 4 0.2000 45 5 11.1091 7.95819 65 31 0.4000 679 6 12.0800 7.32066 22 10 0.2666 249 7 12.7821 6.92008 142 67 0.5108 1870 8 13.3200 6.64181 26 12 0.2000 221 9 14.0223 6.31070 27 13 0.4126 301 10 15.3038 5.78502 40 19 0.3790 367 11 15.9720 5.54447 22 10 0.3760 215 12 16.7906 5.27596 8 4 0.2053 45 13 17.5441 5.05102 16 8 0.3783 144 14 18.4425 4.80695 67 32 0.4050 727 15 19.3884 4.57451 95 45 0.4854 1168 16 19.9200 4.45362 21 10 0.3000 221 17 20.8733 4.25232 23 11 0.7067 437 18 21.9200 4.05157 40 19 0.6400 997 19 22.4800 3.95190 63 30 0.0000 0 20 23.0800 3.85050 75 35 0.6080 1572 21 24.5139 3.62842 145 68 0.7536 2918 22 25.7200 3.46094 56 26 0.3854 641 23 26.4400 3.36830 71 33 0.6000 1054 24 27.1018 3.28754 147 69 0.9236 2866 25 28.6586 3.11239 49 23 0.6507 842 26 29.5960 3.01591 14 7 0.4720 143 27 29.9200 2.98399 7 3 0.2400 51 28 30.6800 2.91178 11 5 0.4000 126 29 32.3200 2.76767 21 10 0.4480 194 30 32.6800 2.73800 25 12 0.7466 350 31 33.2000 2.69629 7 3 0.0000 0 32 36.0700 2.48807 15 7 0.4200 181 33 36.5600 2.45584 7 3 0.2000 62 34 41.8000 2.15929 7 3 0.4000 89 35 43.2000 2.09250 6 3 0.2400 68 Peak Data List for FIG. 22

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 3.6075 24.47248 26 6 0.1650 147 2 3.9600 22.29481 34 7 0.2134 165 3 4.3031 20.51791 80 18 0.3205 723 4 6.2414 14.14964 17 4 0.0611 38 5 7.2400 12.20009 36 8 0.2036 394 6 7.7200 11.44258 426 94 0.3118 3303 7 8.0000 11.04270 330 73 0.2948 2715 8 8.7200 10.13247 54 12 0.4266 848 9 9.6800 9.12964 14 3 0.2900 105 10 9.9628 8.87112 44 10 0.3257 342 11 11.0298 8.01522 57 13 0.3243 526 12 12.3200 7.17858 51 11 0.2400 405 13 12.6400 6.99756 165 36 0.3244 1564 14 13.1212 6.74199 374 82 0.3888 3658 15 13.6800 6.46783 68 15 0.1688 889 16 14.8000 5.98079 18 4 0.0000 0 17 15.3342 5.77362 60 13 0.3396 734 18 15.9420 5.55484 40 9 0.2760 345 19 16.5868 5.34032 202 44 0.3160 1701 20 17.5000 5.06365 24 5 0.1400 105 21 18.0400 4.91328 141 31 0.2892 1111 22 18.4697 4.79993 188 41 0.3518 1617 23 19.4688 4.55580 165 36 0.3205 1292 24 19.9363 4.45001 70 15 0.2726 513 25 20.6000 4.30811 60 13 0.1792 380 26 21.2273 4.18220 455 100 0.3783 4610 27 21.9152 4.05245 15 3 0.0526 39 28 22.6000 3.93118 119 26 0.2830 1096 29 23.2970 3.81512 282 62 0.4626 3282 30 23.8977 3.72057 165 36 0.4917 1965 31 24.4800 3.63337 89 20 0.3152 885 32 25.1600 3.53669 108 24 0.2244 662 33 25.4800 3.49299 86 19 0.3032 1025 34 25.9600 3.42949 57 13 0.0000 0 35 26.6611 3.34087 217 48 0.6191 3485 36 27.8800 3.19752 89 20 0.4492 976 37 28.2400 3.15757 123 27 0.2800 936 38 29.0688 3.06940 94 21 0.2546 702 39 29.5600 3.01950 57 13 0.1400 218 40 29.8400 2.99180 62 14 0.3074 607 41 31.1200 2.87160 48 11 0.4500 530 42 31.5126 2.83672 95 21 0.2739 584 43 31.9200 2.80144 49 11 0.2886 396 44 32.7342 2.73359 66 15 0.4432 626 45 33.2000 2.69629 53 12 0.2978 363 46 33.5500 2.66896 51 11 0.3572 422 47 34.2632 2.61502 25 5 0.1722 163 48 35.3161 2.53943 50 11 0.2477 265 49 35.5392 2.52400 50 11 0.1985 337 50 36.2800 2.47414 35 8 0.0800 163 Peak Data List for FIG. 27

Peak Data List inte- 2Theta d I FWHM grated I No. (degrees) (A) (counts) I/Io (degrees) (counts) 1 3.1200 28.29512 51 10 0.1458 205 2 3.5556 24.82958 38 7 0.0928 186 3 4.3943 20.09228 28 5 0.1014 143 4 4.7950 18.41411 31 6 0.0900 108 5 5.2227 16.90705 16 3 0.0879 43 6 6.6800 13.22154 74 14 0.1482 536 7 7.0596 12.51144 309 58 0.1992 1985 8 8.5211 10.36853 18 3 0.0577 43 9 8.9240 9.90130 16 3 0.0880 67 10 9.4400 9.36121 88 17 0.1866 782 11 9.7646 9.05073 532 100 0.2263 3059 12 10.1600 8.69937 40 8 0.1908 525 13 10.6800 8.27695 38 7 0.1292 176 14 11.0021 8.03534 226 42 0.2376 1509 15 11.3600 7.78298 26 5 0.1150 169 16 13.0470 6.78017 93 17 0.2260 647 17 14.0525 6.29721 246 46 0.3632 2430 18 14.6791 6.02978 71 13 0.2258 452 19 15.5752 5.68482 50 9 0.3238 373 20 15.9988 5.53525 64 12 0.2511 414 21 16.4000 5.40073 43 8 0.1666 204 22 16.7463 5.28982 94 18 0.2474 621 23 17.7700 4.98732 270 51 0.2527 1705 24 18.1200 4.89177 89 17 0.3128 758 25 18.4843 4.79617 109 20 0.2930 804 26 19.0910 4.64510 34 6 0.1321 116 27 20.2740 4.37664 158 30 0.3763 1451 28 20.6400 4.29985 144 27 0.2316 710 29 21.0400 4.21900 133 25 0.4290 1643 30 21.4400 4.14118 231 43 0.2254 1401 31 21.9901 4.03882 37 7 0.2140 187 32 22.2000 4.00110 22 4 0.1600 120 33 22.6083 3.92976 37 7 0.1583 182 34 23.2000 3.83085 49 9 0.1800 331 35 23.6500 3.75897 237 45 0.3000 1961 36 24.0000 3.70494 49 9 0.1494 328 37 24.5063 3.62953 30 6 0.1660 146 38 24.9600 3.56457 64 12 0.2742 540 39 25.5385 3.48512 262 49 0.3049 1992 40 26.0000 3.42430 125 23 0.4572 1443 41 26.6124 3.34687 221 42 0.3039 1600 42 26.9200 3.30933 71 13 0.2266 450 43 27.3600 3.25710 150 28 0.1894 671 44 27.5600 3.23391 167 31 0.3146 1087 45 28.1427 3.16826 104 20 0.5040 1245 46 29.3165 3.04403 28 5 0.1989 191 47 29.7200 3.00361 83 16 0.2000 497 48 30.0400 2.97234 177 33 0.2770 1270 49 30.4000 2.93795 92 17 0.2588 761 50 31.4461 2.84256 20 4 0.1477 154

While specific embodiments of the present invention have been described in the foregoing, it will be appreciated by those skilled in the art that many equivalents, modifications, substitutions, and variations may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims. 

What is claimed is:
 1. A brimonidine pamoate polymorph exhibiting an X-ray powder diffraction spectrum comprising peaks at 2θ angles of 9.7°, 14.6°, 25.9° and 26.5°±0.2°.
 2. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a brimonidine pamoate polymorph of claim
 1. 3. The pharmaceutical composition of claim 2, wherein the pharmaceutically acceptable carrier comprises an aqueous medium.
 4. The pharmaceutical composition of claim 2, wherein the pharmaceutically acceptable carrier comprises an organic medium.
 5. A method for producing the brimonidine pamoate polymorph of claim 1, said method comprising: contacting a brimonidine pamoate polymorph that exhibits an X-ray powder diffraction spectrum comprising peaks at 2θangles of 13.5°, 20.6°, 21.1° and 24.4°±0.2°, with (i) water, or (ii) a mixture of N,N-dimethylformamide and water. 